The SS-N-14 Silex missile is a multipurpose missile designed by the USSR during the Cold War as an anti-submarine weapon. Subsequent variations also introduced an anti-ship mode.
When the weapon was first introduced in the late 1960s, its purpose was unclear. NATO and the USA initially assumed, based on the shape of the launchers, that it was a medium-range anti-shipping missile, probably a derivative of the P-150 Malakhit, better known as the SS-N-9 Siren. It therefore received the next available designation, SS-N-10. This is somewhat understandable - the launchers looked rather like the Malakhit launchers used on Russian missile boats, and they also initially appeared on the Kresta II class destroyer replacing the ASM mountings on the predecessor class. Further, the USSR had just introduced an anti-sub missile into service, the FRAS-1, a rocket tipped with a nuclear depth charge. Some years later, in the mid to late 1970s, it was discovered that Silex was in fact an anti-sub missile, and was redesignated as SS-N-14, the next available designation at the time.
The initial version of the missile was a low-flying subsonic missile, akin to the SS-N-2C Styx, armed with either a nuclear depth charge or a homing torpedo hung under the main missile body (creating an unusual double-bodied look), which flew to its target using inertial guidance. Later, western military intelligence discovered that it had an anti-ship mode. There were a number of theories about how this worked. The most popular notion was that the ASW version of the missile could be fired at a ship exactly as if it were a submarine and drop a torpedo nearby, relying on the torpedo's sonar to find the ship and strike it. This turned out to be wrong. Another idea assumed the addition of an active radar seeker. In this idea, the missile would home in on a ship and strike it, detonating the torpedo's warhead and its hydrogen peroxide fuel, along with the missile's own alcohol fuel. This was also incorrect, though it inspired the Russians to design a weapon very similar to it. The real anti-ship mode carried a bomb under the fuselage in lieu of a torpedo, and used the infrared seeker from SS-N-2C Styx. It was not rated very highly as an anti-ship missile, either by the USA or the USSR. In tests, drones duplicating the Silex's performance were sitting ducks for the American Mk. 45 127mm gun, much less their SAMs.
As an anti-sub missile, however, it was formidable, having superior range to the American ASROC, or the FRAS-1, and a larger torpedo payload than the French Malafon or the Australian Ikara. While never fired in anger, it was THE surface-launched anti-sub missile used in war game scenarios, until it was mostly eclipsed by the SS-N-15 Starfish.
In the late 1980s, after nearly 20 years in service, a new round was introduced, known as Rastrub. The Rastrub carried a shorter-range but large peroxide-fueled torpedo, and intelligence photos showed a clear dome on the missile's nose, indicative of infrared guidance. The initial purpose of this weapon was not known for certain, but analysts suspected that it was a dual-mode anti-surface and anti-sub missile, similar in intended use to the earlier wrong guess about SS-N-14's anti-ship mode. After the Iron Curtain fell in the early 1990s, information from Russian sailors revealed that this was exactly correct. This new round, however, appears not to have entirely replaced the older ones in practice.
The SS-N-14 is perhaps the longest-lived ASW weapon in Russian naval service other than the Type 53 torpedo, and has been used on a number of classes. The standard, well-known quad box launchers comprised the main armament of the Kresta II, Kara, Krivak and Udaloy classes, and was the main anti-sub weapon on the Kirov class cruiser Admiral Ushakov. It remains in service on the Kara, Krivak and Udaloy classes, and is expected to continue to be used for a decade or more.